As a technique capable of preventing an unauthorized duplication of a program, Japanese Patent No. 2569564 discloses a copy protect apparatus of the software. In this copy protect apparatus, since a protect code read out from a floppy disk is not outputted from this copy protect apparatus, it is possible to prohibit an illegal rewriting operation of the software. As a result, it is practically difficult to realize such an operation that the software duplicated in the illegal manner is executable. Thus, the unauthorized duplication of the software can be effectively prevented.
Normally, when a program is developed, a resource such as a library is used which may provide a graphic function and other basic functions. Objects contained in such a resource as a library and the like are not equal to executable modules (load modules). As a result, it is practically difficult to protect against an unauthorized duplication of such a library. As a consequence, software manufacturers provide resources such as libraries to which no copy protection is applied at present stages, while the software manufacturers should necessarily believe good sense of program development persons.